Oracle Fusion Middleware

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1 Oracle Fusion Middleware Programming XML for Oracle WebLogic Server 11g Release 1 (10.3.5) E April 2011 This document is a resource for software developers who design and develop applications that include XML processing.

2 Oracle Fusion Middleware Programming XML for Oracle WebLogic Server, 11g Release 1 (10.3.5) E Copyright 2007, 2011, Oracle and/or its affiliates. All rights reserved. This software and related documentation are provided under a license agreement containing restrictions on use and disclosure and are protected by intellectual property laws. Except as expressly permitted in your license agreement or allowed by law, you may not use, copy, reproduce, translate, broadcast, modify, license, transmit, distribute, exhibit, perform, publish, or display any part, in any form, or by any means. Reverse engineering, disassembly, or decompilation of this software, unless required by law for interoperability, is prohibited. The information contained herein is subject to change without notice and is not warranted to be error-free. If you find any errors, please report them to us in writing. If this software or related documentation is delivered to the U.S. Government or anyone licensing it on behalf of the U.S. Government, the following notice is applicable: U.S. GOVERNMENT RIGHTS Programs, software, databases, and related documentation and technical data delivered to U.S. Government customers are "commercial computer software" or "commercial technical data" pursuant to the applicable Federal Acquisition Regulation and agency-specific supplemental regulations. As such, the use, duplication, disclosure, modification, and adaptation shall be subject to the restrictions and license terms set forth in the applicable Government contract, and, to the extent applicable by the terms of the Government contract, the additional rights set forth in FAR , Commercial Computer Software License (December 2007). Oracle USA, Inc., 500 Oracle Parkway, Redwood City, CA This software is developed for general use in a variety of information management applications. It is not developed or intended for use in any inherently dangerous applications, including applications which may create a risk of personal injury. If you use this software in dangerous applications, then you shall be responsible to take all appropriate fail-safe, backup, redundancy, and other measures to ensure the safe use of this software. Oracle Corporation and its affiliates disclaim any liability for any damages caused by use of this software in dangerous applications. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. This software and documentation may provide access to or information on content, products, and services from third parties. Oracle Corporation and its affiliates are not responsible for and expressly disclaim all warranties of any kind with respect to third-party content, products, and services. Oracle Corporation and its affiliates will not be responsible for any loss, costs, or damages incurred due to your access to or use of third-party content, products, or services.

3 Contents Preface... ix Documentation Accessibility... Conventions... ix ix 1 Introduction and Roadmap 1.1 Document Scope and Audience Guide to This Document Related Documentation Samples for the XML Developer XML Examples in the WebLogic Server Distribution New and Changed XML Features in This Release Summary of WebLogic Server XML Features XML Document Parsers Difference In Default Parsers Between Versions 8.1 and 9.1 of WebLogic Server XML Document Transformer Streaming API for XML (StAX) Implementation WebLogic XPath API JAXP Pluggability Layer Implementation Java API for XML Registries Implementation WebLogic Servlet Attributes WebLogic XSLT JSP Tag Library XML Registry For Configuring Parsers and Transformers XML Registry for Configuring External Entity Resolution Endorsed Standards Override Mechanism for DOM/SAX: Not Supported Learning More About XML XML Overview 2.1 What Is XML? How Do You Describe an XML Document? Why Use XML? What Are XSL and XSLT? What Are DOM and SAX? SAX DOM iii

4 2.6 What Is the Streaming API for XML (StAX)? What Is JAXP? JAXP Packages New Feature of JAXP Common Uses of XML and XSLT Using XML and XSLT to Separate Content from Presentation XML as a Message Format for Business-to-Business Communication Developing XML Applications with WebLogic Server 3.1 Developing XML Applications: Main Steps Parsing XML Documents Parsing XML Documents Using JAXP in SAX Mode Parsing XML Documents Using JAXP in DOM Mode Parsing XML Documents in a Servlet Using the org.xml.sax.defaulthandler Attribute to Parse a Document Using the org.w3c.dom.document Attribute to Parse a Document Validating and Non-Validating Parsers Handling Entity Resolution While Parsing an XML Document General Information About External Entities Using the WebLogic Server Entity Resolution Features Using Parsers Other Than the Default Generating New XML Documents Generating XML from a DOM Document Tree Generating XML Documents in a JSP Transforming XML Documents Using JAXP to Transform XML Data Example of Transforming an XML Document Using JAXP Using the JSP Tag to Transform XML Data XSLT JSP Tag Syntax XSLT JSP Tag Usage Transforming XML Documents Using an XSLT JSP Tag Example of Using the XSLT JSP Tag in a JSP Using Transformers Other Than the Default Transformer Using the Streaming API for XML (StAX) 4.1 Overview of the Streaming API for XML Description of the Cursor API The XMLStreamReader Interface The XMLStreamWriter Interface Description of the Event Iterator API Main Interfaces and Classes of StAX Parsing XML With the XMLStreamReader Interface: Typical Steps Example of Parsing XML Using StAX Getting the XMLStreamReader Object Determining the Specific XML Event Type Getting the Full Name of an Element Getting the Attributes of an Element iv

5 4.2.6 Getting the Namespaces of an Element Getting Text Data Getting Location Information Closing the Input Stream Generating XML Using the XMLStreamWriter Interface: Typical Steps Example of Generating XML Using StAX Getting the XMLStreamWriter Object Adding the XML Declaration to the Output Stream Adding Standard XML Events to the Output Stream Adding Attributes and Namespace Declarations to a Start Element Closing the Output Stream Properties Defined for the XMLInputFactory Interface Properties Defined for the XMLOutputFactory Interface Using Advanced XML APIs 5.1 Using the Java API for XML Registries (JAXR) API Using the WebLogic XPath API Using the DOMXPath Class Example of Using the DOMXPath Class Main Steps When Using the DOMXPath Class Using the StreamXPath Class Example of Using the StreamXPath Class Main Steps When Using the StreamXPath Class XML Programming Best Practices 6.1 When to Use the DOM, SAX, and StAX APIs Increasing Performance of XML Validation When to Use XML Schemas or DTDs Configuring External Entity Resolution for Maximum Performance Using SAX InputSources Improving Performance of Transformations XML Programming Techniques 7.1 Transmitting XML Data Between A Java Client and WebLogic Server Handling XML Documents in a JMS Application Accessing External Entities That Do Not Have an HTTP Interface XML Application Scoping 8.1 Overview of Application Scoping The weblogic-application.xml File xml parser-factory saxparser-factory document-builder-factory transformer-factory v

6 8.2.6 entity-mapping entity-mapping-name public-id system-id entity-uri when-to-cache cache-timeout-interval Configuring a Parser or Transformer for an Enterprise Application Configuring an External Entity for an Enterprise Application Configuring the External Entity Cache for an Enterprise Application Administering WebLogic Server XML 9.1 Overview of Administering WebLogic Server XML XML Administration Tasks How the XML Registry Works Parser Selection Within the XML Registry XML Parser and Transformer Configuration Tasks Configuring a Parser or Transformer Other Than the Default Configuring a Parser for a Particular Document Type External Entity Configuration Tasks Configuring External Entity Resolution Configuring the External Entity Cache A B XML Reference A.1 XML APIs... A-1 A.2 Code Examples... A-1 A.3 Related WebLogic Server Documentation... A-1 A.4 Tutorials and Online Courses... A-1 A.5 Other XML Specifications and Information... A-2 Using the WebLogic XML Streaming API (Deprecated) B.1 Overview of the WebLogic XML Streaming API... B-1 B.2 Javadocs for the WebLogic XML Streaming API... B-2 B.3 Parsing an XML Document: Typical Steps... B-2 B.3.1 Example of Parsing an XML Document... B-3 B.3.2 Getting an XML Input Stream... B-5 B.3.3 Getting a Buffered XML Input Stream... B-5 B.3.4 Filtering the XML Stream... B-6 B.3.5 Creating a Custom Filter... B-7 B.3.6 Iterating Over the Stream... B-8 B.3.7 Determining the Specific XMLEvent Type... B-8 B.3.8 Getting the Attributes of an Element... B-10 B.3.9 Positioning the Stream... B-11 B.3.10 Getting a Substream... B-12 B.3.11 Marking and Resetting a Buffered XML Input Stream... B-13 B.3.12 Closing the Input Stream... B-13 vi

7 B.4 Generating a New XML Document: Typical Steps... B-13 B.4.1 Example of Generating an XML Document... B-14 B.4.2 Creating an XML Output Stream... B-16 B.4.3 Adding Elements to the Output Stream... B-17 B.4.4 Adding Attributes to an Element on the Output Stream... B-17 B.4.5 Adding an Input Stream to an Output Stream... B-18 B.4.6 Printing an Output Stream... B-18 B.4.7 Closing the Output Stream... B-19 vii

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9 Preface This preface describes the document accessibility features and conventions used in this guide Programming XML for Oracle WebLogic Server. Documentation Accessibility Our goal is to make Oracle products, services, and supporting documentation accessible to all users, including users that are disabled. To that end, our documentation includes features that make information available to users of assistive technology. This documentation is available in HTML format, and contains markup to facilitate access by the disabled community. Accessibility standards will continue to evolve over time, and Oracle is actively engaged with other market-leading technology vendors to address technical obstacles so that our documentation can be accessible to all of our customers. For more information, visit the Oracle Accessibility Program Web site at Accessibility of Code Examples in Documentation Screen readers may not always correctly read the code examples in this document. The conventions for writing code require that closing braces should appear on an otherwise empty line; however, some screen readers may not always read a line of text that consists solely of a bracket or brace. Accessibility of Links to External Web Sites in Documentation This documentation may contain links to Web sites of other companies or organizations that Oracle does not own or control. Oracle neither evaluates nor makes any representations regarding the accessibility of these Web sites. Access to Oracle Support Oracle customers have access to electronic support through My Oracle Support. For information, visit or visit if you are hearing impaired. Conventions The following text conventions are used in this document: Convention boldface Meaning Boldface type indicates graphical user interface elements associated with an action, or terms defined in text or the glossary. ix

10 Convention italic monospace Meaning Italic type indicates book titles, emphasis, or placeholder variables for which you supply particular values. Monospace type indicates commands within a paragraph, URLs, code in examples, text that appears on the screen, or text that you enter. x

11 1 1Introduction and Roadmap This section describes the contents and organization of this guide Programming XML for Oracle WebLogic Server. Section 1.1, "Document Scope and Audience" Section 1.2, "Guide to This Document" Section 1.3, "Related Documentation" Section 1.5, "New and Changed XML Features in This Release" Section 1.6, "Summary of WebLogic Server XML Features" Section 1.7, "Endorsed Standards Override Mechanism for DOM/SAX: Not Supported" Section 1.8, "Learning More About XML" 1.1 Document Scope and Audience This document is a resource for software developers who design and develop applications that include XML processing. The topics in this document are relevant during the design and development phases of a software project. The document also includes topics that are useful in solving application problems that are discovered during test and pre-production phases of a project. Although this document does include administration and monitoring information useful to developers who want to test their applications in a development environment, the document does not address production-phase administration, monitoring, or performance tuning topics XML topics. For links to WebLogic Server documentation and resources for these topics, see Section 1.3, "Related Documentation." It is assumed that the reader is familiar with Web technologies, XML, XSLT, the Java programming language, and the Servlet and JSP APIs of the J2EE specification. This document emphasizes the value-added features provided by WebLogic Server XML and key information about how to use WebLogic Server features and facilities to get an application that performs XML processing up and running. 1.2 Guide to This Document This document is organized as follows: Introduction and Roadmap 1-1

12 Related Documentation This chapter, Chapter 1, "Introduction and Roadmap," introduces the organization of this guide and the features of WebLogic Server XML. Chapter 2, "XML Overview," provides an overview of XML technology and the WebLogic Server XML subsystem. Chapter 3, "Developing XML Applications with WebLogic Server," describes how to process XML documents from within a WebLogic Server application using XML APIs and tools. The main processing tasks include parsing an existing XML document, generating a new XML document, and transforming a XML document into another format. Chapter 4, "Using the Streaming API for XML (StAX)," describes in detail how to use the Streaming API for XML (StAX) in your Java applications to parse and generate an XML document. Chapter 5, "Using Advanced XML APIs," describes how to use additional XML APIs to do more advanced tasks, such as performing XPath matching against an XML document. Chapter 6, "XML Programming Best Practices," describes some best practices to follow when creating Java applications that process XML documents. Chapter 7, "XML Programming Techniques," describes specific programming techniques for tasks such as using message-driven beans and JMS queues with XML documents, and so on. Chapter 8, "XML Application Scoping," describes how to configure parsers, transformers, and external entities for a particular Enterprise application. Chapter 9, "Administering WebLogic Server XML," describes the Administration Console XML Registry and how to perform XML configuration tasks. Appendix A, "XML Reference," provides pointers to specifications and application programming interfaces supported by the XML software. Appendix B, "Using the WebLogic XML Streaming API (Deprecated)," describes how to use the deprecated WebLogic XML Streaming API. The topic is included in this guide for legacy reasons only; you should not use this API for new applications. Instead you should use StAX, described in Chapter 4, "Using the Streaming API for XML (StAX)." 1.3 Related Documentation This document contains XML-specific design and development information. For comprehensive guidelines for developing, deploying, and monitoring WebLogic Server applications, see the following documents: Developing Applications for Oracle WebLogic Server is a guide to developing WebLogic Server components (such as Web applications and EJBs) and applications. Getting Started With JAX-WS Web Services for Oracle WebLogic Server is a guide to developing Web Services that are deployed and run on WebLogic Server. Deploying Applications to Oracle WebLogic Server is the primary source of information about deploying WebLogic Server applications. For related information about XML outside the scope of this document, see links listed in Section 1.8, "Learning More About XML" and Appendix A, "XML Reference." 1-2 Programming XML for Oracle WebLogic Server

13 Summary of WebLogic Server XML Features 1.4 Samples for the XML Developer In addition to this document, Oracle provides a variety of code samples for XML developers. The examples and tutorials illustrate WebLogic Server XML in action, and provide practical instructions on how to perform key XML development tasks. Oracle recommends that you run some or all of the XML examples before programming your own application that processes XML XML Examples in the WebLogic Server Distribution WebLogic Server optionally installs API code examples in WL_ HOME\samples\server\examples\src\examples, where WL_HOME is the top-level directory of your WebLogic Server installation. You can start the examples server, and obtain information about the samples and how to run them from the WebLogic Server Start menu. 1.5 New and Changed XML Features in This Release For a comprehensive listing of the new WebLogic Server features introduced in this release, see What s New in Oracle WebLogic Server. 1.6 Summary of WebLogic Server XML Features WebLogic Server consolidates XML technologies applicable to WebLogic Server and XML applications based on WebLogic Server. The WebLogic Server XML subsystem allows customers to use standard parsers, the WebLogic FastParser, XSLT transformers, and DTDs and XML Schemas to process and convert XML files. The following topics, which describe the features included in the WebLogic Server XML subsystem, are presented in this section: XML Document Parsers Section 1.6.1, "XML Document Parsers" Section 1.6.2, "XML Document Transformer" Section 1.6.3, "Streaming API for XML (StAX) Implementation" Section 1.6.4, "WebLogic XPath API" Section 1.6.5, "JAXP Pluggability Layer Implementation" Section 1.6.6, "Java API for XML Registries Implementation" Section 1.6.7, "WebLogic Servlet Attributes" Section 1.6.8, "WebLogic XSLT JSP Tag Library" Section 1.6.9, "XML Registry For Configuring Parsers and Transformers" Section , "XML Registry for Configuring External Entity Resolution" WebLogic Server uses, by default, the XML parser that is included in the JDK Version 5.0. You can also use any other XML parser of your choice by using the Administration Console to configure it in the XML Registry. You can configure a single instance of WebLogic Server to use one parser for a particular application and use another parser for a different application. Introduction and Roadmap 1-3

14 Summary of WebLogic Server XML Features For information about parsing XML documents, see Section 3.2, "Parsing XML Documents." Difference In Default Parsers Between Versions 8.1 and 9.1 of WebLogic Server The default parser in Versions 8.1and previous of WebLogic Server was one that was based on Apache's Xerces parser and whose package name started with weblogic.apache.xerces.*. In Version 9.1 of WebLogic Server, this parser has been deprecated. Instead, the default parser is the same one that is shipped in JDK 5.0. For backward compatibility, the weblogic.apache.xerces.* parser is still available in Version 9.1 of WebLogic Server, although it is deprecated and Oracle highly recommends you do not use it since it will not be available in future versions. If, however, you need to temporarily continue using this parser, you must use the Administration Console to configure a parser other than the default for your WebLogic Server instance by updating, or creating, a new XML Registry and setting the default implementation classes for SAX and DOM parser factory interfaces, as indicated in Table 1 1. Table 1 1 Parser Factory Interface Default Implementation Classes for SAX and DOM Parser Factory Interfaces DOM (DocumentBuilderFactory) SAX (SAXParserFactory) Implementation Class weblogic.apache.xerces.jaxp.documentbuilderfactoryimpl weblogic.apache.xerces.jaxp.saxparserfactoryimpl For information about creating an XML Registry, see Chapter 9, "Administering WebLogic Server XML." XML Document Transformer WebLogic Server uses, by default, the XML transformer that is included in the JDK Version 5.0. You can also use any other XML transformer of your choice by using the Administration Console to configure it in the XML Registry. You can configure a single instance of WebLogic Server to use one transformer for a particular application and use another transformer for a different application. For more information about transforming XML documents, see Section 3.4, "Transforming XML Documents." Streaming API for XML (StAX) Implementation WebLogic XPath API WebLogic Server includes an implementation of the Streaming API for XML (StAX). For more information, see Chapter 4, "Using the Streaming API for XML (StAX)." The WebLogic XPath API contains all of the classes required to perform XPath matching against a document represented as a DOM, an XMLInputStream, or an XMLOutputStream. For more information, see Section 5.2, "Using the WebLogic XPath API." 1-4 Programming XML for Oracle WebLogic Server

15 Summary of WebLogic Server XML Features JAXP Pluggability Layer Implementation Java API for XML Processing (JAXP) 1.2 is a Java-standard, parser-independent API for XML. For more information on JAXP, see Section 2.7, "What Is JAXP?." Note: WebLogic Server uses the XML Registry, accessed through the Administration Console, to plug in parsers and transformers. This is different from the JAXP 1.2 specification which specifies the use of system properties to plug in parsers and transformers Java API for XML Registries Implementation The Java API for XML Registries (JAXR) API, described at provides a uniform and standard Java API for accessing different kinds of registries, in particular XML registries used in Web Service applications. For more information, see Section 5.1, "Using the Java API for XML Registries (JAXR) API." WebLogic Servlet Attributes WebLogic Server supports the following special Servlet attributes: org.xml.sax.handlerbase org.xml.sax.helpers.defaulthandler org.w3c.dom.document Calling the setattribute (for SAX parsing) and getattribute (for DOM parsing) methods on a ServletRequest object with the preceding attributes will parse any given XML document. For more information, see Section 3.2.3, "Parsing XML Documents in a Servlet." WebLogic XSLT JSP Tag Library The JSP tag library provides a simple tag that enables access to the default XSLT transformer from within a Java Server Page (JSP) running on WebLogic Server. Currently, this tag supports the default XSLT transformer only; you cannot use the tag to transform an XML document from within a JSP using a different transformer. The JSP tag library is included in xmlx-tags.jar, which is installed when you install your WebLogic Server distribution. For more information, see Section 3.4.3, "Using the JSP Tag to Transform XML Data." XML Registry For Configuring Parsers and Transformers The XML Registry simplifies administration and configuration tasks by separating these tasks from the XML application. Use the Administration Console to configure the parsers and transformers for an instance of WebLogic Server. For more information, see Section 9.2, "XML Parser and Transformer Configuration Tasks." Introduction and Roadmap 1-5

16 Endorsed Standards Override Mechanism for DOM/SAX: Not Supported XML Registry for Configuring External Entity Resolution WebLogic XML supports external entity resolution through the XML Registry. For more information, see Section 9.3, "External Entity Configuration Tasks." 1.7 Endorsed Standards Override Mechanism for DOM/SAX: Not Supported WebLogic Server does not support switching the server's DOM and SAX interfaces using the endorsed standards override mechanism. An endorsed standard is a Java API defined through a standards process other than the Java Community Process (JCP). For more information, see Endorsed Standards Override Mechanism at Learning More About XML To learn more about XML, see the following online courses and tutorials. Appendix A, "XML Reference," provides links to additional information. A Technical Introduction to XML, available at XML Authoring Tutorial, available at Working with XML and Java, available at Tutorials for using the Java 2 platform and XML technology, available at XML, Java, and the Future of the Web, available at Chapter 17 of The XML Bible: XSL Transformations, available at XSL Tutorial by Miloslav Nic, available at tml SAX 2.0: The Simple API for XML, available at Document Object Model (DOM), available at Programming XML for Oracle WebLogic Server

17 2 2XML Overview The following sections provide an overview of XML technology and the WebLogic Server XML subsystem: Section 2.1, "What Is XML?" Section 2.2, "How Do You Describe an XML Document?" Section 2.3, "Why Use XML?" Section 2.4, "What Are XSL and XSLT?" Section 2.5, "What Are DOM and SAX?" Section 2.6, "What Is the Streaming API for XML (StAX)?" Section 2.7, "What Is JAXP?" Section 2.8, "Common Uses of XML and XSLT" 2.1 What Is XML? Extensible Markup Language (XML) is a markup language used to describe the content and structure of data in a document. It is a simplified version of Standard Generalized Markup Language (SGML). XML is an industry standard for delivering content on the Internet. Because it provides a facility to define new tags, XML is also extensible. Like HTML, XML uses tags to describe content. However, rather than focusing on the presentation of content, the tags in XML describe the meaning and hierarchical structure of data. This functionality allows for the sophisticated data types that are required for efficient data interchange between different programs and systems. Further, because XML enables separation of content and presentation, the content, or data, is portable across heterogeneous systems. The XML syntax uses matching start and end tags (such as <name> and </name>) to mark up information. Information delimited by tags is called an element. Every XML document has a single root element, which is the top-level element that contains all the other elements. Elements that are contained by other elements are often referred to as sub-elements. An element can optionally have attributes, structured as name-value pairs, that are part of the element and are used to further define it. The following sample XML file describes the contents of an address book: <?xml version="1.0"?> <address_book> <person gender="f"> <name>jane Doe</name> XML Overview 2-1

18 How Do You Describe an XML Document? <address> <street>123 Main St.</street> <city>san Francisco</city> <state>ca</state> <zip>94117</zip> </address> <phone area_code=415> </phone> </person> <person gender="m"> <name>john Smith</name> <phone area_code=510> </phone> </person> </address_book> The root element of the XML file is address_book. The address book currently contains two entries in the form of person elements: Jane Doe and John Smith. Jane Doe's entry includes her address and phone number; John Smith's includes his phone and address. Note that the structure of the XML document defines the phone element as storing the area code using the area_code attribute rather than a sub-element in the body of the element. Also note that not all sub-elements are required for the person element. 2.2 How Do You Describe an XML Document? There are two ways to describe an XML document: XML Schemas and DTDs. XML Schemas define the basic requirements for the structure of a particular XML document. A Schema describes the elements and attributes that are valid in an XML document, and the contexts in which they are valid. In other words, a Schema specifies which tags are allowed within certain other tags, and which tags and attributes are optional. Schemas are themselves XML files. The schema specification is a product of the World Wide Web Consortium (W3C). For detailed information on XML schemas, see The following example shows a schema that describes the preceding address book sample XML document: <xsd:schema xmlns:xsd=" <xsd:complextype name="persontype"> <xsd:element name="name" type="xsd:string"/> <xsd:element name="address" type="addresstype"/> <xsd:element name="phone" type="phonetype"/> <xsd:element name=" " type="xsd:string"/> <xsd:attribute name="gender" type="xsd:string"/> </xsd:complextype> <xsd:complextype name="addresstype"> <xsd:element name="street" type="xsd:string"/> <xsd:element name="city" type="xsd:string"/> <xsd:element name="state" type="xsd:string"/> <xsd:element name="zip" type="xsd:string"/> </xsd:complextype> <xsd:simpletype name="phonetype"> <xsd:restriction base="xsd:string"/> <xsd:attribute name="area_code" type="xsd:string"/> 2-2 Programming XML for Oracle WebLogic Server

19 Why Use XML? </xsd:simpletype> </xsd:schema> You can also describe XML documents using Document Type Definition (DTD) files, a technology older than XML Schemas. DTDs are not XML files. The following example shows a DTD that describes the preceding address book sample XML document: <!DOCTYPE address_book [ <!ELEMENT person (name, address?, phone?, ?)> <!ELEMENT name (#PCDATA)> <!ELEMENT address (street, city, state, zip)> <!ELEMENT phone (#PCDATA)> <!ELEMENT (#PCDATA)> <!ELEMENT street (#PCDATA)> <!ELEMENT city (#PCDATA)> <!ELEMENT state (#PCDATA)> <!ELEMENT zip (#PCDATA)> <!ATTLIST person gender CDATA #REQUIRED> <!ATTLIST phone area_code CDATA #REQUIRED> ]> An XML document can include a Schema or DTD as part of the document itself, reference an external Schema or DTD, or not include or reference a Schema or DTD at all. The following excerpt from an XML document shows how to reference an external DTD called address.dtd: <?xml version=1.0?> <!DOCTYPE address_book SYSTEM "address.dtd"> <address_book>... XML documents only need to be accompanied by Schema or DTD if they need to be validated by a parser or if they contain complex types. An XML document is considered valid if 1) it has an associated Schema or DTD, and 2) it complies with the constraints expressed in the associated Schema or DTD. If, however, an XML document only needs to be well-formed, then the document does not have to be accompanied by a Schema or DTD. A document is considered well-formed if it follows all the rules in the W3C Recommendation for XML 1.0. For the full XML 1.0 specification, see Why Use XML? An industry typically uses data exchange methods that are meaningful and specific to that industry. With the advent of e-commerce, businesses conduct an increasing number of relationships with a variety of industries and, therefore, must develop expert knowledge of the various protocols used by those industries for electronic communication. The extensibility of XML makes it a very effective tool for standardizing the format of data interchange among various industries. For example, when message brokers and workflow engines must coordinate transactions among multiple industries or departments within an enterprise, they can use XML to combine data from disparate sources into a format that is understandable by all parties. XML Overview 2-3

20 What Are XSL and XSLT? 2.4 What Are XSL and XSLT? The Extensible Stylesheet Language (XSL) is a W3C standard for describing presentation rules that apply to XML documents. XSL includes both a transformation language, (XSLT), and a formatting language. These two languages function independently of each other. XSLT is an XML-based language and W3C specification that describes how to transform an XML document into another XML document, or into HTML, PDF, or some other document format. An XSLT transformer accepts as input an XML document and an XSLT document. The template rules contained in an XSLT document include patterns that specify the XML tree to which the rule applies. The XSLT transformer scans the XML document for patterns that match the rule, and then it applies the template to the appropriate section of the original XML document. 2.5 What Are DOM and SAX? DOM and SAX are two standard Java application programming interfaces (APIs) for parsing XML data. Both are supported by the WebLogic Server default parser. The two APIs differ in their approach to parsing, with each API having its strengths and weaknesses SAX DOM SAX stands for the Simple API for XML. It is a platform-independent language neutral standard interface for event-based XML parsing. SAX defines events that can occur as a parser is reading through an XML document, such as the start or the end of an element. Programmers provide handlers to deal with different events as the document is parsed. Programmers that use the SAX API to parse XML documents have full control over what happens when these events occur and can, as a result, customize the parsing process extensively. For example, a programmer might decide to stop parsing an XML document as soon as the parser encounters an error that indicates that the document is invalid, rather than waiting until the entire document is parsed, thus improving performance. The WebLogic Server default parser (the parser included in the JDK 5.0) supports SAX Version 2.0. Programmers who have created programs that use Version 1.0 of SAX to parse XML documents should read about the changes between the two versions and update their programs accordingly. For detailed information about the differences between the two versions, refer to DOM stands for the Document Object Model. It is platform- and language-neutral interface that allows programs and scripts to access and update the content, structure, and style of XML documents dynamically. DOM reads an XML document into memory and represents it as a tree; each node of the tree represents a particular piece of data from the original XML document. Because the tree structure is a standard programming mechanism for representing data, traversing and manipulating the tree using Java is relatively easy, fast, and efficient. The main drawback, however, is that the entire XML document has to be read into memory for DOM to create the tree, which might decrease the performance of an application as the XML documents get larger. 2-4 Programming XML for Oracle WebLogic Server

21 What Is JAXP? The WebLogic Server default parser (the parser included in the JDK 5.0) supports DOM Level 2.0 Core. Programmers who have created programs that use Level 1.0 of DOM to parse XML documents should read about the changes between the two versions and update their programs accordingly. For detailed information about the differences, refer to What Is the Streaming API for XML (StAX)? In addition to SAX and DOM, you can also parse and generate an XML document using the Streaming API for XML (StAX). StAX is Java Community Process specification that describes a bi-directional API for reading and writing XML. StAX gives parsing control to the programmer by exposing a simple iterator-based API and an underlying stream of events; the API includes methods such as next() and hasnext() that allow the programmer to ask for the next event rather than handle the event in a callback. This gives the programmer more procedural control over the processing of the XML document. Unlike DOM and SAX, StAX is not yet part of the Java API for XML Processing (JAXP). Note: Previous versions of WebLogic Server included a similar proprietary API called WebLogic XML Streaming API. This API was a basis for StAX. Although the WebLogic XML Streaming API is still accessible in this release of WebLogic Server, its functionality has been deprecated as of release 9.0 of WebLogic Server. Programmers should use StAX instead. 2.7 What Is JAXP? JAXP Packages For detailed information about using StAX, see Chapter 4, "Using the Streaming API for XML (StAX)." The previous section discusses two APIs, SAX and DOM, that programmers can use to parse XML data. The Java API for XML Processing (JAXP) provides a means to get to these parsers. JAXP also defines a pluggability layer that allows programmers to use any compliant parser or transformer. WebLogic Server implements JAXP to facilitate XML application development and the work required to move XML applications built on WebLogic Server to other Web application servers. JAXP was developed by Sun Microsystems to make XML applications portable; it provides basic support for parsing and transforming XML documents through a standardized set of Java platform APIs. JAXP 1.2, included in the WebLogic Server distribution, is configured to use the default parser. Therefore, by default, XML applications built using WebLogic Server use JAXP. The WebLogic Server distribution contains the interfaces and classes needed for JAXP 1.2. JAXP 1.2 contains explicit support for SAX Version 2 and DOM Level 2. JAXP contains the following two packages: javax.xml.parsers javax.xml.transform XML Overview 2-5

22 Common Uses of XML and XSLT The javax.xml.parsers package contains the classes to parse XML data in SAX Version 2.0 and DOM Level 2.0 mode. To parse an XML document in SAX mode, a programmer first instantiates a new SaxParserFactory object with the newinstance() method. This method looks up the specific implementation of the parser to load based on a well-defined list of locations. The programmer then obtains a SaxParser instance from the SaxParserFactory and executes its parse() method, passing it the XML document to be parsed. Parsing an XML document in DOM mode is similar, except that the programmer uses the DocumentBuilder and DocumentBuilderFactory classes instead. For detailed information on using JAXP to parse XML documents, see Section 3.2, "Parsing XML Documents." The javax.xml.transform package contains classes to transform XML data, such as an XML document, a DOM tree, or SAX events, into a different format. The transformer classes work similarly to the parser classes. To transform an XML document, a programmer first instantiates a TransformerFactory object with the newinstance() method. This method looks up the specific implementation of the XSLT transformer to load based on a well-defined list of locations. The programmer then instantiates a new Transformer object based on a specific XSLT style sheet and executes its transform() method, passing it the XML object to transform. The XML object might be an XML file, a DOM tree, and so on. For detailed information on using JAXP to transform XML objects, see Section 3.4.1, "Using JAXP to Transform XML Data." New Feature of JAXP 1.2 J2EE 1.4 includes version 1.2 of JAXP, which is based on the 1.1 version, but adds support for W3C XML Schema. In particular, the 1.2 version specifies new property strings to enable XML Schema validation, specify the schema language being used, and the location of the particular XML Schema file that should be used when validating an XML file. The following code snippet shows how to set Schema validation when using a SAX parser: try { SAXParserFactory spf = SAXParserFactory.newInstance(); spf.setnamespaceaware(true); spf.setvalidating(true); SAXParser sp = spf.newsaxparser(); sp.setproperty(" " sp.setproperty(" " DefaultHandler dh = new DefaultHandler(); sp.parse(" dh); catch(saxexception se) { se.printstacktrace(); For more information, see the JAXP 1.2 Approved Changes at Common Uses of XML and XSLT How you use XML and XSLT depends on your particular business needs. 2-6 Programming XML for Oracle WebLogic Server

23 Common Uses of XML and XSLT Using XML and XSLT to Separate Content from Presentation XML and XSLT are often used in applications that support multiple client types. For example, suppose you have a Web-based application that supports both browser-based clients and Wireless Application Protocol (WAP) clients. These clients understand different markup languages, HTML and Wireless Markup Language (WML), respectively, but your application must deliver content that is appropriate for both. To accomplish this goal, you can write your application to first produce an XML document that represents the data it is sending to the client. Then the application can transform the XML document that represents the data into HTML or WML, depending on the client's browser type. Your application can determine the client browser type by examining the User-Agent request header of an HTTP request. Once the application knows the client browser type, it uses the appropriate XSLT style sheet to transform the document into the correct markup language. See the SnoopServlet example included in the examples/servlets directory of your WebLogic Server distribution for an example of how to access this type of header information. This method of rendering the same XML document using different markup languages in respective client types helps concentrate the effort required to support multiple client types into the development of the appropriate XSLT style sheets. Additionally, it allows your application to adapt to other clients types easily, if necessary. For additional information about XSLT, see Section A.5, "Other XML Specifications and Information." XML as a Message Format for Business-to-Business Communication In a business-to-business (B2B) environment, Company A and Company B want to exchange information about e-commerce transactions in which both are involved. Company A is a major e-commerce site. Company B is a small affiliate that sells Company A's products to a niche group of customers. When Company B sends customers to Company A, Company B is compensated in two ways: it receives, from Company A, both money and information about other customers that make the same sort of purchases as those made by the customers referred by Company B. To exchange information, Company A and Company B must agree on a data format for information that is machine readable and that operates with systems from both companies easily. XML is the logical data format to use in this scenario, but selecting this format is only the first step. The companies must then agree on the format of the XML messages to be exchanged. Because Company A has a one-to-many relationship with its affiliates, Company A must define the format of the XML messages that will be exchanged. To define the format of XML messages, or XML documents, Company A creates two document type definitions (DTDs): one that describes the information that A will provide about customers and one that describes the information that A wants to receive about a newly affiliated company. Company B must also create two DTDs: one to process the XML documents received from Company A and one to prepare an XML document in a format that can be processed by Company A. XML Overview 2-7

24 Common Uses of XML and XSLT 2-8 Programming XML for Oracle WebLogic Server

25 3 3Developing XML Applications with WebLogic Server The following sections describe how to use the Java programming language and WebLogic Server to develop XML applications. It is assumed that you know how to use Java Servlets and Java Server Pages (JSPs) to write Java applications. For information about how to write servlet and JSP applications, see Developing Web Applications, Servlets, and JSPs for Oracle WebLogic Server. Section 3.1, "Developing XML Applications: Main Steps" Section 3.2, "Parsing XML Documents" Section 3.3, "Generating New XML Documents" Section 3.4, "Transforming XML Documents" 3.1 Developing XML Applications: Main Steps Programmers using the WebLogic Server XML subsystem typically perform some or all of the following programming tasks when developing XML applications: 1. Parse an XML document. The XML document can originate from a number of sources. For example, a programmer might develop a servlet to receive an XML document from a client, write an EJB to receive an XML document from a Servlet or another EJB, and so on. In each instance, the XML document may have to be parsed so that its data can be manipulated. For more information on this task, refer to Section 3.2, "Parsing XML Documents." 2. Generate a new XML document. After a servlet or EJB has received and parsed an XML document and possibly manipulated the data in some way, the Servlet or EJB might need to generate a new XML document to send back to the client or to pass on to another EJB. For more information on this task, refer to Section 3.3, "Generating New XML Documents." 3. Transform XML data into another format. After parsing an XML document or generating a new one, the Servlet or EJB may need to transform it into another format, such as HTML, WML, or plain text. For more information on this task, refer to Section 3.4.1, "Using JAXP to Transform XML Data." Developing XML Applications with WebLogic Server 3-1

26 Parsing XML Documents 3.2 Parsing XML Documents This section describes how to parse XML documents using JAXP in both DOM and SAX mode and how to parse XML documents from a servlet. Note: For detailed instructions on using the Streaming API for XML (StAX) to parse XML documents, see Chapter 4, "Using the Streaming API for XML (StAX)." You use the Administration Console XML Registry to configure the following: Per-document-type parsers, which supersede the default parser for the specified document type. External entity resolution, or the process that an XML parser goes through when requested to find an external file in the course of parsing an XML document For detailed information on how to use the Administration Console for these tasks, refer to Chapter 9, "Administering WebLogic Server XML." Parsing XML Documents Using JAXP in SAX Mode The following code example shows how to configure a SAX parser factory to create a validating parser. The example also shows how to register the MyHandler class with the parser. The MyHandler class can override any method of the DefaultHandler class to provide custom behavior for SAX parsing events or errors. import javax.xml.parsers.saxparser; import javax.xml.parsers.saxparserfactory;... MyHandler handler = new MyHandler(); // MyHandler extends org.xml.sax.helpers.defaulthandler. //Obtain an instance of SAXParserFactory. SAXParserFactory spf = SAXParserFactory.newInstance(); //Specify a validating parser. spf.setvalidating(true); // Requires loading the DTD. //Obtain an instance of a SAX parser from the factory. SAXParser sp = spf.newsaxparser(); //Parse the documnt. sp.parse(" handler);... Note: If you want to use a parser other than the default parser, you must use the WebLogic Server Administration Console to specify the parser in the XML Registry; otherwise the SaxParserFactory.newInstance method returns the default parser. For instructions about configuring WebLogic Server to use a parser other than the default parser, see Section 9.2.1, "Configuring a Parser or Transformer Other Than the Default." Parsing XML Documents Using JAXP in DOM Mode The following code example shows how to parse an XML document and create an org.w3c.dom.document tree from a DocumentBuilder object: 3-2 Programming XML for Oracle WebLogic Server

27 Parsing XML Documents import javax.xml.parsers.documentbuilder; import javax.xml.parsers.documentbuilderfactory; import org.w3c.dom.document;... //Obtain an instance of DocumentBuilderFactory. DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); //Specify a validating parser. dbf.setvalidating(true); // Requires loading the DTD. //Obtain an instance of a DocumentBuilder from the factory. DocumentBuilder db = dbf.newdocumentbuilder(); //Parse the document. Document doc = db.parse(inputfile);... Note: If you want to use a parser other than the default parser, you must use the WebLogic Server Administration Console to specify it; otherwise the DocumentBuilderFactory.newInstance method returns the default parser. For instructions about configuring WebLogic Server to use a parser other than the default parser, see Section 9.2.1, "Configuring a Parser or Transformer Other Than the Default." Parsing XML Documents in a Servlet Support for the setattribute and getattribute methods was added to version 2.2 of the Java Servlet Specification. Attributes are objects associated with a request. The request object encapsulates all information from the client request. In the HTTP protocol, this information is transmitted from the client to the server by the HTTP headers and message body of the request. With WebLogic Server, you can use the setattribute and getattribute methods to parse XML documents. Use the setattribute method for SAX mode parsing and the getattribute method for DOM mode parsing, as described in Section 3.2.4, "Using the org.xml.sax.defaulthandler Attribute to Parse a Document" and Section 3.2.5, "Using the org.w3c.dom.document Attribute to Parse a Document." Before you can use the setattribute and getattribute methods, however, you must configure a WebLogic Server servlet filter called weblogic.servlet.xmlparsinghelper (deployed by default on all WebLogic Server instances) as part of your Web application. Configure the servlet filter by adding the following elements to the web.xml deployment descriptor, located in the WEB-INF directory of your Web application: <filter> <filter-name>xmlparsinghelper</filter-name> <filter-class>weblogic.servlet.xmlparsinghelper</filter-class> </filter> <filter-mapping> <filter-name>xmlparsinghelper</filter-name> <url-pattern>/*</url-pattern> <dispatcher>request</dispatcher> </filter-mapping> Developing XML Applications with WebLogic Server 3-3